A vacuum chamber is a structure enclosing an interior in a fluid-sealed manner such that the interior may be maintained at a desired vacuum-level fluid pressure. The structure may include one or more walls defining the boundaries of the interior. The ambient pressure of the environment external to the vacuum chamber may be a much higher pressure, for example atmospheric pressure (760 Torr). Thus, the pressure differential across the chamber wall(s) may be quite large, spanning several orders of magnitude for example. The force imparted to the chamber wall is proportional to the exposed surface area of the chamber wall and the pressure differential, F=A(PATM−PVAC), and will induce stress and strain in the chamber wall. When the size of the vacuum chamber is large compared to the thickness of its walls, the forces experienced due to the pressure differential will induce strains on the walls capable of causing large deformations in the walls, for example on the order of a few micrometers (μm) to hundreds of micrometers (a fraction of a millimeter (mm)).
Analytical instruments utilize vacuum chambers to facilitate the operation of charged particle optics components (or simply “optics”) in controlling particle motion, such as shaping, steering, accelerating, or decelerating a charged particle beam, for example an ion beam, electron beam, etc. For such applications, one or more charged particle optics components may be mounted to the inside of one or more walls of the vacuum chamber. The charged particle optics often require precise alignments, with alignment tolerances on the order of one or more micrometers to tens of micrometers. A deformation of the chamber wall may cause a misalignment in the charged particle optics.
One example of such an analytical instrument is a mass spectrometry (MS) system, which analyzes a sample of interest to produce a mass spectrum, i.e., a series of peaks indicative of the relative abundances of detected ions as a function of their mass-to-charge ratios (also referred to more briefly as “m/z ratios,” or more simply as “masses”). The MS system typically includes, in order of process flow, an ion source for ionizing molecules of the sample, followed by one or more intermediate ion processing devices providing various functions, followed by a mass analyzer for separating ions based on their differing m/z ratios, followed by an ion detector at which the mass-sorted ions arrive. The ion source may operate at vacuum or atmospheric pressure, depending on design. The rest of the devices in the sequence include vacuum chambers. The vacuum chambers are in fluid communication with a vacuum system via sealed interfaces. The vacuum system includes one or more vacuum pumps, which may be a combination of different types of pumps as needed to achieve the required vacuum levels. The vacuum system is configured to provide independently controlled vacuum-level gas pressures in the respective vacuum chambers. The vacuum system may be operated such that each chamber successively reduces the gas pressure below the level of the preceding chamber, ultimately down to the very low pressure (very high vacuum) required for operating the mass analyzer (e.g., ranging from 10−4 to 10−9 Torr). Thus, the MS system directs an ion beam through one or more vacuum chambers and ultimately to the vacuum chamber containing the mass analyzer. For this purpose, various ion optics are mounted in the vacuum chambers. In vacuum chambers susceptible to deformation, the ion optics must be mounted in a manner that sufficiently isolates them from the deformation. Otherwise, the ion optics may be moved out of proper alignment and adversely affect control of the ion beam, which may result in loss of ions, impaired and/or inaccurate beam transmission, degradation of the analytical data acquired, and other problems.
Therefore, there is a need for isolating charged particle optics from deformations of the vacuum chamber in which the charged particle optics are mounted.